Genome-wide identification and expression profiling of the dehydrin gene family in Actinidia chinensis

Dehydrins (DHNs) play a vital role in enhancing plant tolerance to abiotic stresses. In kiwifruit, there has not been a comprehensive and systematic study undertaken on the DHN gene family to date. In this study, seven AcDHNs were identified and cloned in kiwifruit, which were divided into two subgroups, YnSKn- and SKn-types. AcDHN2/AcDHN7 and AcDHN4/AcDHN5 originated evolutionarily from segmental duplication. AcDHN2 and AcDHN7 were highly expressed in leaves, stems, roots, and fruits. During leaf growth, the expression levels of AcDHN1, AcDHN4 and AcDHN5 were downregulated; during fruit growth, AcDHN1 and AcDHN6 were upregulated, while AcDHN4 and AcDHN5 were downregulated. These findings suggest that these genes may be involved in the regulation of leaf or fruit development. Under various abiotic stresses (drought, high and low temperatures, and salt stress) and abscisic acid treatment, the transcription levels of AcDHN1, AcDHN2, AcDHN6, and AcDHN7 were significantly increased. AcDHN3 was only induced by low temperature stress, and AcDHN4 and AcDHN5 only slightly responded to high temperature and salt stress. These results lay a foundation for further study of their function under various stress conditions.